Fuel additives ?

[kevin b]

I like to "play" with ic engines occasionally and recently have been given an old Laser 75. Jon has been very helpful with information (I asked before taking it to bits !) and it should be an interesting project as I have no experience with Lasers.

This got me thinking about old engines generally and how we look after them. My background is automotive and goes back to when electronic fuel injection was being introduced in exotic motor cars.

Back then we would regularly use fuel additives in our engines for various reasons and it got me thinking about our model engines. For instance a petrol 2 stroke is more or less the same, whether it is 10cc, or 250cc (wet, or dry sump).

So I thought I would ask the question. Have any of you got experience of the effects of additives in model engine fuel (apart from nitro), using STP, Redex, Wynns etc to chemically clean the engine without dismantling it ? Not just petrol, but glow and diesel as well.

It's not that I would want to do this (I enjoy tinkering), but I thought it might make an interesting topic for discussion.

[Chris Walby]

Not a model engine, but a highly stressed air cooled racing 2 stroke running on petrol at about 14:1 (about as far as you can go on static timing without it knocking).

Most people at that time were running Castrol R or Castrol M and the advent of the Japanese with reed/power valves was upon us. Anyway the Castrol R was a killer if people messed around on the start line and once oiled your race was screwed (left dead on the line and no joy until the plug was changed).

Then someone mentioned using Bel-Ray synthetic (MC-1 IIIRC) and wow it was great! Started easier, ran way cleaner and good performance. Come the next strip down and the rings were truly shot, but less wear on the bore and somewhere between dad and me we missed something out on re-assembly.

Next few races it went like stink as fast as the sister engine on methanol that had bigger ports and higher compression. At the next service same again rings shot, but the bore was ok, so my dad said to pass him the copper head gasket and he would anneal it while I got the barrel back on......but there isn't one I said, well it needs it if running on petrol (omitted for methanol use), then the penny dropped.

We had run half a season on petrol and very high compression, then on careful examination of the packaging for the oil one of the benefits was an included octane booster.

Back to your OP, if the engine is designed and has the right materials in it to withstand additional power then crank it up, but IIRC Jon does not advise the lower oil for the older engines. If that's the case you will just kill a decent engine as parts aren't available, but if looked after could last many years.

I obtained a 62, checked it over and popped it in a trainer, now have extra enjoyment while teaching and listening to a lovely Laser at 1/4 to 1/2 throttle. Ok it says Nova 40, but they really meant 62 four stroke !

PS - some of the more unusual additives can be very corrosive to certain metals or react violently, but normally it just destroys parts.

Edited By Chris Walby on 04/01/2021 15:18:49

[Engine Doctor]

A friend and I once tried dripping Slick 50 into the air intake of an old DC Saber while it was running. The engine was well worn with just enough compression to get it started. After running for 20 minutes or so the compression was greatly improved and lasted well.

Apparently Slick 50 was bought by a bigger company and formula changed and is now rubbish. I've never tried any other additives.

I have wondered if modern diesel additives would help with starting some model diesel engines but the smell of them has put me off .

[Maurice Dyer]

I have been running everything from Cox .020c.f. to fill size Pratt and Whitney Gas turbines ( it was part of my job).

Additive 1. Correct fuel.

Additive 2. Manufacturers operating procedure adhered to.

Additive 3. A brain.

No probs.😃

[Peter Christy]

You have to remember that anything you *add* displaces fuel, and it is the fuel that generates the power.

Modern synthetic oils are very good at keeping the insides of our engines spotless - unlike castor - and can even clean up engines lacquered with castor residue - eventually!

In short, if you are running a good brand of fully synthetic oil in your motor, there should be no need for any additive. Indeed it may be counter-productive!

--

Pete

[Simon Chaddock]

Like putting oil in the fuel of a model plane 4 stroke for lubrication!

[Rich Griff]

Anyone successfully ran a 2t model engine with petrol?

I did a bench test on a Magnum gp40, well run in.

It ran well on petrol ( may have been leaded or LRP at the time, 1990's ) with 2t oil at about 15 to one and the glow permanently powered.

It was an experiment to see if it would.

I know you can get miniature spark plugs that fit the glow heads....

[Alan Gorham_]

OS make special glow plugs that will catalyse and ignite petrol based fuels. They make a couple of dedicated engines, but some people have had success with large 2 strokes (such as the Moki range) on petrol and such plugs.

**LINK**

[John Stainforth]

Has anyone else noticed how those more expensive car diesel fuels with additives (e.g., Shell V-power, or BP Ulitmate, or whatever they are called) give slightly lower performance and mpg than the cheaper fuels without the additives?

[Engine Doctor]

Hi Its a bit off topic for models engines , but hey .I don't know about the expensive car diesel fuels as never use them . I have always used supermarket diesel and never had a problem . I then started to use a diesel additive in my current car , Millers Ecomax . I started using it due to these modern diesels possibly suffering from DPF problems when used on short runs . The Ecomax gives noticeable increase in performance and makes engine feel smoother and quieter. On my older cars I used to add two stroke oil to the fuel and this again made engine feel smoother and quieter. Neither of these affected the MPG but worth using IMO to keep injectors and EGR valve etc clean.

[Phil McCavity]

Posted by John Stainforth on 06/01/2021 17:23:47:

Has anyone else noticed how those more expensive car diesel fuels with additives (e.g., Shell V-power, or BP Ulitmate, or whatever they are called) give slightly lower performance and mpg than the cheaper fuels without the additives?

On the contrary, if I don't run my petrol car on V-Power or Momentum the ECU adapts to restrict power, the owners manual recommends to use a minimum octane above 95 and 99 for max performance.

[Martin Harris - Moderator]

Posted by John Stainforth on 06/01/2021 17:23:47:

Has anyone else noticed how those more expensive car diesel fuels with additives (e.g., Shell V-power, or BP Ulitmate, or whatever they are called) give slightly lower performance and mpg than the cheaper fuels without the additives?

I haven't noticed much difference at all, but I have only used them for the tank before an MOT test in the (probably very false) hope that the emission levels may have been slightly improved if they happened to be borderline.

The main benefit (at present) of these fuels is the lower (and possibly still with Esso, zero) levels of ethanol in them.

This was not the case back around the early 90s when Shell introduced a new version of their 4 star. I'm sure there was no placebo effect as a week or two before it was announced, my 3 litre Reliant Scimitar suddenly started running about 3 mpg better - quite noticeable when you're refilling a 17gallon tank every week! This improvement was maintained until it was withdrawn after complaints that some cars were experiencing valve damage when using it.

Back on topic, I do use them for petrol engines in models (and other small engines) due to their (claimed) better long term stability.

Edited By Martin Harris - Moderator on 07/01/2021 15:13:58

[Phil McCavity]

Posted by Martin Harris - Moderator on 07/01/2021 15:11:08:

Posted by John Stainforth on 06/01/2021 17:23:47:

Has anyone else noticed how those more expensive car diesel fuels with additives (e.g., Shell V-power, or BP Ulitmate, or whatever they are called) give slightly lower performance and mpg than the cheaper fuels without the additives?

I haven't noticed much difference at all, but I have only used them for the tank before an MOT test in the (probably very false) hope that the emission levels may have been slightly improved if they happened to be borderline.

If your emissions are borderline an 'Italian tune' will lower them prior to the MOT.

[John Stainforth]

I can usually tell within about five miles of refueling whether I have better or worse fuel in the tank just by how the car feels. I also watch my mpg gauge all the time. The effect of the fuel additives I mentioned is fairly subtle (a few mpg on my diesel Golfs, e.g. 65 mpg compared with 68), but the effect of added ethanol on my petrol car is somewhat more pronounced. In America, petrol with 10% ethanol is called E10, and I found by monitoring the effects over every single tankful for fifteen years that the mpg with the ethanol is about 7% worse than without it. Some petrol ('gas' stations in the area I lived in added the ethanol, and some did not, and not all consistently did or did not add ethanol. Again, after just a few miles, I could always tell whether I had a tank with or without ethanol. (My typical mpg in my Prius with the ethanol was about 44 and 47 without).

Edited By John Stainforth on 07/01/2021 16:42:27